The present invention broadly relates to a pipe coupling comprising a housing which can be clamped about pipe ends which are to be interconnected and which possesses radially inwardly flexed or turned end flanges.
Generally speaking, the pipe coupling is of the type where within the housing there is enclosed an inwardly open sealing gasket possessing a substantially C-shaped axial cross-sectional configuration and made from an elastomeric material such as synthetic rubber. Both ends of this sealing gasket are supported upon the inner or confronting jacket surface of a respective truncated cone-shaped or frusto-conical clamping ring whose diameter can be reduced. Each of the frusto-conical clamping rings is retained at its outer edge or outer region in the axial direction within the housing and is provided with an inner edge or inner region which mechanically engages the periphery of the pipe ends to be interconnected.
A pipe coupling of the aforesaid type is described in the Swiss Pat. No. 620,510, which is substantially cognate with the German Pat. No. 2,731,464, published Mar. 9, 1978 and with the U.S. Pat. No. 4,108,479, granted Aug. 22, 1978. This known pipe coupling has proved itself in practice. The clamping rings are laminated in the region of their smaller or minor diameter by means of straight or J-shaped incisions and the lamellae are somewhat twisted at least at one of their side edges so that the lamellae overlap one another to a certain degree in an imbricated fashion. In such manner the lamellae form claws or teeth on the inner edge or inner region of the clamping rings which dig into the outer surfaces of the pipes to be interconnected during clamping of the housing. These claws or teeth form a substantial snug-fit between the ends of the pipes to be interconnected by means of the housing of the pipe coupling on which the clamping rings are supported.
The ends of the lamellae or teeth for digging into the outer surfaces of the pipes of the known pipe coupling are formed by means of a flat front surface which is practically at right angles to the inner and outer jacket surfaces of the truncated cone-shaped or frusto-conical clamping rings.
It is observed that if the aforesaid known pipe coupling were used to interconnect the ends of pipes made from a comparatively hard material, for example cast iron, a substantial force would be necessary for clamping the housing until the inner edge or inner region of the clamping rings had reliably and sufficiently dug into the outer surfaces around the peripheries of the pipes.
Likewise it is observed that if the aforesaid known pipe coupling were employed to interconnect the ends of pipes made from a comparatively soft material capable of creeping, for example aluminum or copper, the force required for clamping the housing until the inner edge or inner region of the clamping rings had dug into the pipe ends is in fact substantially lower. The depth of penetration of the lamellae or teeth on the inner edge or inner region of the clamping rings, however, remains undetermined or indefinite, so that, especially with very thin-walled pipes, these clamping rings are subject to a possible weakening of their grip into the outer periphery of the pipe ends at the contact line of the inner edge or inner region of the clamping rings.